gh-106727: Add __module__ check for inspect.getsource(cls)

[gaogaotiantian]

In method heuristics, make sure the method we check against comes from the same file as the class. Fixed the issue from #106815

• Issue: inspect.getsource (findsource) not working as expected when duplicate class is used #106727

[gaogaotiantian]

This fix is straightforward enough and is a supplement to #106815, so I skipped the news. If @carljm thinks the other way, I can add the news. Also do we want a test for it? It requires some delicate file line number conflict from two files.

[carljm]

Can we add a test that fails without this fix?

This doesn't fix the case I mentioned (metaclass and class using it, both with the same name and in the same module), but it does fix the case where the metaclass is in a different module and the line numbers just happen to collide with another class of the same name.

I'm not seeing a clear way to fix the "metaclass with same name" case, and I'm also not really worried about it.

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[carljm]

This fix is straightforward enough and is a supplement to #106815, so I skipped the news. If @carljm thinks the other way, I can add the news. Also do we want a test for it? It requires some delicate file line number conflict from two files.

Oops, this comment crossed with my review. I think skipping news is fine, but I think we should have a test, even though it requires additional files. Subtle cases like this will break again in future refactors if there's no test. If it's worth fixing, it's worth testing.

[gaogaotiantian]

Fixed the style and added the test case - used a temporary directory for the files so I don't need to add extra files to the source code. Without the new check, the code would've found the first class as the line number of method borrowed from the other module happens to be inside the first class defined in inspect_actual.

Confirmed that the test would fail without the new check.